U.S. patent number 11,441,605 [Application Number 17/188,249] was granted by the patent office on 2022-09-13 for dual-film damper.
This patent grant is currently assigned to PRATT & WHITNEY CANADA CORP.. The grantee listed for this patent is PRATT & WHITNEY CANADA CORP.. Invention is credited to David Beamish, Mert Cevik, Robert J. Morris, Philip A. Varney.
United States Patent |
11,441,605 |
Cevik , et al. |
September 13, 2022 |
Dual-film damper
Abstract
A dual-film damper has a housing defining an annular damper
fluidly connected to a source of pressurized oil. First and second
damper rings are coaxially nested within the damper cavity. A first
set of spacers allows for the formation of a first oil film annulus
between the first and second damper rings. A second set of spacers
allows for the formation of a second oil film annulus between the
second damper ring and the housing. The first and second oil film
annuli have a thickness-to-length ratio (T/L) selected to provide a
desired damping capacity.
Inventors: |
Cevik; Mert (Boucherville,
CA), Varney; Philip A. (Coventry, CT), Morris;
Robert J. (Jasper, GA), Beamish; David (Mississauga,
CA) |
Applicant: |
Name |
City |
State |
Country |
Type |
PRATT & WHITNEY CANADA CORP. |
Longueuil |
N/A |
CA |
|
|
Assignee: |
PRATT & WHITNEY CANADA
CORP. (Longueuil, CA)
|
Family
ID: |
1000006557367 |
Appl.
No.: |
17/188,249 |
Filed: |
March 1, 2021 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F16F
15/0237 (20130101); F01D 25/164 (20130101); F16C
27/045 (20130101); F16C 2360/23 (20130101) |
Current International
Class: |
F16C
27/04 (20060101); F16F 15/023 (20060101); F01D
25/16 (20060101) |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Pilkington; James
Attorney, Agent or Firm: Norton Rose Fulbright Canada
LLP.
Claims
What is claimed is:
1. A dual-film damper in a gas turbine engine, comprising: a
housing circumscribing an annular damper cavity around an axis and
having an oil inlet connectable in flow communication with a source
of pressurized oil; a first and a second damper ring coaxially
nested within the annular damper cavity; a first pair of axially
spaced-apart spacers positioned radially between the first and
second damper rings, the first pair of axially spaced-apart spacers
creating a first oil film annulus between the first and second
damper rings; and a second pair of axially spaced-apart spacers
radially between the second damper ring and the housing, the second
set of spacers creating a second oil film annulus between the
second damper ring and the housing, the second oil film annulus
surrounding the first oil film annulus; each of the first and
second oil film annuli having a thickness-to-length ratio (T/L)
ranging from 0.0025 to 0.03.
2. The dual-film damper according to claim 1, wherein the first oil
film annulus has a thickness T1, wherein the second oil film
annulus has a thickness T2, and wherein T1/T2 is between 0.5 and
5.
3. The dual-film damper according to claim 2, wherein the thickness
T1 of the first oil film annulus ranges from 5 mils (0.127 mm) to
30 mils (0.762 mm), and wherein the thickness T2 of the second film
annulus ranges from 2.5 mils (0.0635 mm) to 45 mils (1.143 mm).
4. The dual-film damper according to claim 2, wherein the first and
second oil film annuli have the same length (L).
5. The dual-film damper according to claim 1, wherein the
thickness-to-length ratio (T/L) ranges from 0.0053 to 0.025.
6. The dual-film damper according to claim 1, wherein the first and
second oil film annuli have the same thickness-to-length ratio
(T/L).
7. The dual-film damper according to claim 1, wherein the first
damper ring is an outer race of a bearing.
8. The dual-film damper according to claim 1, wherein the first and
second oil film annuli have a length L ranging from 1000 mils (25.4
mm) to 1500 mils (38.1 mm) mm, and wherein the first and second oil
film annuli have a thickness T ranging from 8 mils (0.203 mm) mm to
25 mils (0.635 mm).
9. The dual-film damper according to claim 1, wherein the first and
second oil film annuli have a length L range from 1000 mils (25.4
mm) mm to 2000 mils (50.8 mm), wherein the first oil film annulus
has a thickness T1 ranging from 5 mils (0.127 mm) to 30 mils (0.762
mm) and wherein the second oil film annulus has a thickness T2
ranging from 2.5 mils (0.063 mm) to 45 mils (1.143 mm).
10. A dual-film damper for damping radial movement of a rotary
shaft relative to a rotation axis, the dual-film damper comprising:
a housing defining an oil damper cavity around the rotation axis;
at most two coaxially nested damper rings including first and
second damper rings disposed in the oil damper cavity; a first
annulus located radially between the first and second damper rings;
a second annulus located radially between the second damper ring
and the housing, the second annulus encircling the first annulus;
and a first and a second pair of axially spaced-apart piston rings
projecting respectively radially across the first annulus and the
second annulus, the first and second pairs of axially spaced-apart
piston rings defining a thickness T and a length L of the first
annulus and the second annulus, respectively; wherein a
thickness-to-length ratio (T/L) ranges from 0.0053 to 0.025.
11. The dual-film damper according to claim 10, wherein the length
L ranges from 1000 mils (25.4 mm) to 1500 mils (38.1 mm), and
wherein the thickness T ranges from 8 mils (0.203 mm) to 25 mils
(0.635 mm).
12. The dual-film damper according to claim 11, wherein the first
annulus and the second annulus have the same length L and the same
thickness T.
13. The dual-film damper according to claim 12, wherein the
thickness T is equal to 16 mils (0.406 mm).
14. The dual-film damper according to claim 10, wherein the first
damper ring is an outer race of a bearing.
15. A dual-film damper for damping radial movement of a rotary
shaft relative to a rotation axis, the dual-film damper comprising:
a housing defining an oil damper cavity around the rotation axis;
at most two damper rings including first and second damper rings
disposed in the oil damper cavity, the second damper ring
encircling the first damper ring; a first oil film annulus located
radially between the first and second damper rings; a second oil
film annulus located radially between the second damper ring and
the housing; and a first and a second pair of spacer rings
respectively projecting radially across the first oil film annulus
and the second oil film annulus, the first and second pairs of
spacer rings respectively defining a thickness T and a length L of
the first oil film annulus and the second oil film annulus, wherein
the length L ranges from 1000 mils (25.4 mm) to 2000 mils (50.8
mm), wherein the thickness T of the first oil film annulus ranges
from 5 mils (0.127 mm) to 30 mils (0.762 mm), and wherein the
thickness T of the second oil film annulus ranges from 2.5 mils
(0.051 mm) to 45 mils (1.143 mm).
16. The dual-film damper according to claim 15, wherein the first
oil film annulus has a first thickness T1, the second oil film
annulus has a second thickness T2, and wherein T1/T2 is between 0.5
and 5.
17. The dual-film damper according to claim 15, wherein the first
and second oil film annuli have a different thickness-to-length
ratio (T/L).
18. The dual-film damper according to claim 15, wherein the first
and second oil film annuli have the same length L.
19. The dual-film damper according to claim 15, wherein the first
damper ring is an outer race of a bearing.
20. The dual-film damper according to claim 15, wherein the
thickness T of the first oil film annulus is equal to the thickness
of the second oil film annulus.
Description
TECHNICAL FIELD
The disclosure relates to dampers for reducing vibrations in a
rotor system and, more particularly, to squeeze film dampers.
BACKGROUND
Squeeze film dampers with a single oil film are well known and used
throughout the gas turbine and turbomachinery industry. They are
typically placed in series with the rotor system bearing supports
to reduce vibrations that would otherwise be present in the system.
In some instances (i.e. high rotor unbalance), a large amount of
damping is needed beyond what a single film damper is capable of
providing so multi-film dampers are used.
However, the use of multi-film dampers with 3 or more oil films
(layers) bring challenges related to mechanical integrity.
Alternatives are thus desirable.
SUMMARY
In one aspect, the disclosure describes a dual-film damper in a gas
turbine engine, comprising: a housing circumscribing an annular
damper cavity around an axis and having an oil inlet connectable in
flow communication with a source of pressurized oil; first and
second damper rings coaxially nested within the annular damper
cavity; a first pair of axially spaced-apart spacers radially
between the first and second damper rings, the first pair of
axially spaced-apart spacers creating a first oil film annulus
between the first and second damper rings; and a second pair of
axially spaced-apart spacers radially between the second damper
ring and the housing, the second set of spacers creating a second
oil film annulus between the second damper ring and the housing,
the second oil film annulus surrounding the first oil film annulus;
the first and second oil film annuli having a thickness-to-length
ratio (T/L) ranging from 0.0025 to 0.03.
In a further aspect, the disclosure describes a dual-film damper
for damping radial movement of a rotary shaft relative to a
rotation axis, the dual-film damper comprising: a housing defining
an oil damper cavity around the rotation axis; at most two
coaxially nested damper rings including first and second damper
rings disposed in the oil damper cavity; a first annulus radially
between the first and second damper rings; a second annulus
radially between the second damper ring and the housing, the second
annulus encircling the first annulus; and a first and a second pair
of axially spaced-apart piston rings projecting respectively
radially across the first annulus and the second annulus, the first
and second pairs of axially spaced-apart piston rings defining a
thickness T and a length L of the first annulus and the second
annulus, respectively; wherein a thickness-to-length ratio (T/L)
ranges from 0.0053 to 0.025.
In accordance with a still further aspect, there is provided a
dual-film damper for damping radial movement of a rotary shaft
relative to a rotation axis, the dual-film damper comprising: a
housing defining an oil damper cavity around the rotation axis; at
most two damper rings including first and second damper rings
disposed in the oil damper cavity, the second damper ring
encircling the first damper ring; a first oil film annulus radially
between the first and second damper rings; a second oil film
annulus radially between the second damper ring and the housing;
and first and second pairs of spacer rings respectively projecting
radially across the first oil film annulus and the second oil film
annulus, the first and second pairs of spacer rings respectively
defining a thickness T and a length L of the first oil film annulus
and the second oil film annulus, wherein L ranges from 1000 mils
(25.4 mm) to 2000 mils (50.8 mm), wherein the thickness of the
first oil film annulus ranges from 5 mils (0.127 mm) to 30 mils
(0.762 mm), and wherein the thickness of the second oil film
annulus ranges from 2.5 mils (0.051 mm) to 45 mils (1.143 mm).
DESCRIPTION OF THE DRAWINGS
FIG. 1 shows an axial cross-section view of an exemplary turbofan
engine including a dual-film damper; and
FIG. 2 is a schematic sectional view through an exemplary
dual-large clearance film damper along an axial radial plane of the
engine.
DETAILED DESCRIPTION
FIG. 1 shows an axial cross-section through an example turbo-fan
gas turbine engine. Air intake into the engine passes over fan
blades 1 in a fan case 2 and is then split into an outer annular
flow through the bypass duct 3 and an inner flow through the
low-pressure axial compressor 4 and high-pressure centrifugal
compressor 5. Compressed air exits the compressor through a
diffuser 6 and is contained within a plenum 7 that surrounds the
combustor 8. Fuel is supplied to the combustor 8 through fuel tubes
9 and fuel is mixed with air from the plenum 7 when sprayed through
nozzles into the combustor 8 as a fuel air mixture that is ignited.
A portion of the compressed air within the plenum 7 is admitted
into the combustor 8 through orifices in the side walls to create a
cooling air curtain along the combustor walls or is used for
cooling to eventually mix with the hot gases from the combustor and
pass over the nozzle guide vane 10 and turbines 11 before exiting
the tail of the engine as exhaust.
The engine 10 includes several rotor structures. For instance, the
engine 10 can be provided in the form of a twin-spool engine
comprising a low pressure spool and a high pressure spool mounted
for rotation about the engine centerline CL. In use, such rotor
structures are subject to vibrations, which needs to be dampened.
In some applications, the amount of damping required is too large
for a conventional single film damper. While multi-film dampers
with three or more oil film layers could be used to provide
additional damping, it has been found that the more multi-film
layers are used, the more the dampers are vulnerable to structural
issues. Such structural issues may lead to premature wear of the
dampers and, thus, ultimately compromise the integrity of the rotor
system. Applicant tests on multi-film dampers (3 or more layers)
showed that high deflection associated with high unbalance causes
damage on seals and damper rings which potentially leads premature
failures in engine structure. Further investigations at test rig
level showed that the high deflection also causes significant oil
leak and aeration of the outer bearing race in multi-film
configurations. It is thus suitable to minimize the number of oil
film layers. The inventors have found that contrary to what could
be expected, the damping capacity of a multi-film oil damper may be
increased by increasing the oil thickness of the oil films within a
predetermined range and by limiting the number of oil films/layers
to two. As will be seen hereinafter with respect to some
embodiments of a dual-film damper, an increase film thickness range
and a film thickness-to-length ratio can be set to allow a
dual-film damper to have a damping capacity comparable to
multi-film dampers with 3 or more layers.
Now referring back to FIG. 1, there is shown a stationary forward
bearing housing 12 that supports a low pressure spool shaft 15
(FIG. 2) with a roller bearing 13 (see FIG. 2). As can be
appreciated from FIG. 2, the roller bearing 13 includes a dual-film
damper 14. The dual-film damper 14 is provided to accommodate
radial movement of the rotary shaft 15 relative to the stationary
bearing housing 12. More particularly, the dual-film damper 14
provides damping to the low pressure spool shaft 15 to reduce
vibrations. While the dual-film damper 14 is herein described in
the context of a low pressure spool, it is understood that the
dual-film damper 14 could be used in conjunction with other rotor
systems (e.g. the high pressure spool) of the engine 10, the low
pressure spool being only one possible application.
As shown in FIG. 2, the exemplified dual-film damper 14 includes an
annular damper cavity 17 defined within the bearing housing 12
between a radially outward wall 18, a first radially extending side
wall 19 and a second radially extending side wall 20. The damper
cavity 17 has an oil inlet 21 fluidly connected to a source of
pressurized oil, such as an engine oil circulating pump. According
to an embodiment, the oil inlet 21 can include inlet openings 21a,
21b defined in the second side wall 20. However, it is understood
that various oil supply arrangements could be used. The exemplified
oil inlet 21 is provided for illustration purposes only.
Still referring to FIG. 2, the dual-damper 14 comprises at most two
damper rings including a first and a second damper ring 22, 24
coaxially nested in the damper cavity 17 about shaft 15. The first
damper ring 22, in the embodiment shown, serves both as an outer
race for the rollers 23 of roller bearing 13 and to contain the
pressurized oil within the damper cavity 17. The second and last
damper ring 24 is disposed radially between the first damper ring
22 and the radially outward wall 18 of the bearing housing 12. The
first and second damper rings 22, 24 extend axially between opposed
axial ends. According to some embodiments, the first and second
damper rings 22, 24 have a same axial length. The length of the two
damper rings 22, 24 can generally correspond to that of the damper
cavity 17. According to some embodiments, the opposed axial ends of
the damper rings 22, 24 radially slidably sealed with the first and
second radially extending side walls 19, 20 of the annular damper
cavity 17 to contain the oil in the damper cavity 17.
Still referring to FIG. 2, a spacer 26 is disposed at each axial
end portion of each damper ring 22, 24 (i.e. on opposed sides of a
central/mid-point location along an axial length of the damper
rings). According to some embodiments, the spacers 26 are provided
in the form of removable spacer rings, such as piston rings,
O-rings or the like removably mounted in corresponding annular
grooves defined in the radially outer cylindrical surface of the
first and second damper rings 22, 24. For instance, each spacer 26
can take the form of a metallic split ring attached to the outer
diameter of a damper ring. Alternatively, the spacers 26 could be
integrally formed with the damper rings 22, 24. For instance, the
spacers could take the form of annular projections extending
integrally from the inner and/or the outer radial surface of the
damper rings 22, 24.
The spacers 26 serve to create first and second annuli 30, 32 that
are filled with oil flow under pressure to thereby create a pair of
coaxially nested oil film annuli in the damper cavity 17. The
spacers 26 maintain a minimum space/clearance between the first and
second damper rings 22, 24 and the second damper ring 24 and the
end wall 18 of the housing 12. In other words, the spacers 26 set
the thickness of the first and second oil film annuli 30, 32 in a
radial direction relative to the engine centerline CL. According
the illustrated embodiment, the first and second oil film annuli
30, 32 have a same thickness T. However, it is understood that the
first and second oil film annuli 30, 32 could have a different
thickness. According to some embodiments, the thickness T ranges
from 8 mils to 25 mils (8 thousandth of an inch to 25 thousandth of
an inch that is 0.203 mm to 0.635 mm). By so increasing the
thickness of the annuli 30, 32 (i.e. the thickness of the oil
films/layers) relative to the oil film thickness of conventional
multi-film dampers, it is possible to obtain added damping capacity
with a reduced number of oil films. With such an increase in
clearance between the damper rings (i.e. increase in the radial
thickness T of the nested oil film annuli), the damping capacity
can be improved with only two oil film annuli. According to a
further embodiment, the film damper is a dual film damper with two
identical 16 mils (0.406 mm) oil film annuli (T=16 mils). According
to other embodiments, the thickness T1 of the first oil film annuli
30 is comprised between 5 mils (0.127 mm) and 30 mils (0.762 mm),
whereas the thickness T2 of the second oil film annuli 32 is
between 2.5 mils (0.058 mm) and 45 mils 1.143 mm).
As shown in FIG. 2, the first and second oil film annuli 30, 32
have an axial length L generally corresponding to the
center-to-center distance between respective pairs of spacers 26.
According to the illustrated embodiment, the first and second oil
film annuli 30, 32 have a same axial L. However, it is understood
that the first and second oil film annuli 30, 32 could have a
different length. According to some embodiments, the length L is
between 1000 mils and 2000 mils (1 inch-1.5 inches) (25.4 mm and
50.8 mm). According to some applications, an optimum range for the
Length L is comprised between 1000 mils (25.4 mm) and 1500 mils
(38.1 mm).
According to some embodiments, damping capacity gains have been
obtained with dual film dampers having a thickness-to-length ratio
(T/L) ranging from 0.0025 to 0.03. For applications where the first
and second oil film annuli 30, 32 have a same thickness T and a
same length L, the thickness-to-length ratio can vary from 0.0053
to 0.025. For instance, the T/L ratio can be defined as follows:
L=1000 L=1500 T=8 0.008 0.0053 T=25 0.025 0.0166
For applications where the thickness T of the first and second oil
film annuli 30, 32 have different boundary values, the
thickness-to-length ratio of the first oil film annuli 30 can vary
from 0.0025 to 0.03. For instance, the T/L ratio of the first oil
film annuli 30 can be defined as follows: L=1000 L=2000 T1=5 0.005
0.0025 T1=30 0.03 0.015
And the ratio of the thickness T1 of the first oil film annuli 30
to the thickness T2 of the second oil film annuli 32 (T1/T2) can
range from 0.5 to 5.
Such relation between the thickest T and the length L of the first
and second oil film annuli 30, 32 allows to increase the damping
capacity compared to conventional single film dampers without being
exposed to the adverse effects of high deflection as encountered
with typical multi-film dampers with 3 or more damper rings.
According to one embodiment, the first and second oil film annuli
30, 32 have a same thickness-to-length ratio. According to other
embodiments, the first and second oil film annuli 30, 32 have a
different thickness-to-length ratio.
In view of the foregoing, it can be appreciated that at least some
of the above describes embodiments addresses some of the challenges
relating to the mechanical integrity of multi-film dampers.
According to at least some embodiments, the structural shortcomings
of multi-film dampers are at least partly overcome through the use
of a dual film damper with increase film clearance. For instance,
the inventors have found that by having two films with a large oil
film clearance (oil film increased thickness), damping capacity can
be increased compared to a single film damper and that without
being exposed to the adverse effects of high deflection in a
typical multi-film damper design having 3 or more oil films
(layers). The earlier multi-film damper designs do not introduce
advantage of larger oil film clearance as a factor to increase
damper capacity, hence mitigate the disadvantage of using limited
number of films.
The above description is meant to be exemplary only, and one
skilled in the relevant arts will recognize that changes may be
made to the embodiments described without departing from the scope
of the invention disclosed. The present disclosure may be embodied
in other specific forms without departing from the subject matter
of the claims. The present disclosure is intended to cover and
embrace all suitable changes in technology. Modifications which
fall within the scope of the present invention will be apparent to
those skilled in the art, in light of a review of this disclosure,
and such modifications are intended to fall within the appended
claims. Also, the scope of the claims should not be limited by the
preferred embodiments set forth in the examples, but should be
given the broadest interpretation consistent with the description
as a whole.
* * * * *